Process and apparatus for preparing extracts and oils from plants and other matter

ABSTRACT

The invention relates to a process for extracting fixed and mineral oils, and/or essential oils, from materials using a process of solvent extraction which is performed under pressure. The solvent is iodotrifluoromethane or iodotrifluoromethane in combination with a co-solvent. The invention also relates to an apparatus for performing the extraction of fixed and mineral oils, and/or essential oils. Substantial reductions in or elimination of the normally high latent heat of solvent evaporation may also be achieved simply by raising or lowering the temperature of or simply by adding or removing “sensible” heat from the solvent at appropriate points during its re-circulation.

The present invention relates to a method of extracting andconcentrating oils from materials in which the oils are alreadydispersed. More particularly, the present invention is concerned withthe extraction of fixed and mineral oils and/or volatile oils such asessential oils from materials using a process of solvent extractionwhich is performed under pressure.

The term “Fixed Oil” is usually used to describe oils of vegetable oranimal origin which are not volatile oils. They routinely comprisenatural mixtures of mono-, di and tri-glycerides, fatty acids, sterols(and their esters) and natural waxes.

“Mineral Oil” is a term usually used to describe petrochemical oilsoften derived from below ground level, which are normally mixtures ofaliphatic and aromatic hydrocarbons of a very wide variety of chainlength and molecular weight. These oils are often the sources oflubricating and fuel oils.

The term “Essential Oil” is usually used to describe those volatile oilsof low molecular weight which incorporate the fragrance and flavour ofcomponents derived from plant materials.

In an earlier application (GB 2276392) we described the use of HFC 134A(1, 1, 1, 2-tetrafluoroethane) as a solvent for the extraction ofessential oils from natural sources.

However HFC 134a is in fact a very poor solvent for many compounds,particularly less volatile compounds. Thus, whilst HFC 134a is able todissolve some essential oils thereby facilitating extraction of suchoils from plant-based materials, this solvent is not able easily todissolve compounds of lower volatility such as fixed oils. HFC 134a istherefore capable at ambient temperatures of extracting only very highquality fragrant and aromatic essential oils i.e. delicate oils of highvolatility and low molecular weight and it will not dissolve the fixedoils which are also frequently associated with these components in thenatural raw material.

Because HFC 134a is a very poor solvent, large quantities of it must beused in order to obtain a commercially acceptable yield of the desirablecomponent extracted from most raw materials.

In another unpublished application (GB 9905054.4) we describe a processin which HFC 134a is used to extract fixed and mineral oils from asubstance. This process relies on the unexpected finding that raisingthe temperature only a few degrees Celsius results in a marked increasein the solubility of fixed and mineral oils in HFC 134a. The process isconducted in a sealed apparatus including a first vessel in which thesubstance is contacted with HFC 134a at an elevated temperature and asecond vessel in which the HFC 134a (now containing dissolved fixed ormineral oil) is cooled. The fixed or mineral oil is precipitated out ofthe solution and can easily be separated from the HFC 134a solvent whichis then recycled to minimise losses and environmental impact.

In a variation of the process described in our unpublished applicationGB 9905054.4, the solvent may be a mixture of HFC 134a and a co-solventin which the fixed or mineral oil to be extracted is relatively soluble.The dissolving properties of HFC 134a are significantly increased by theaddition of a suitable co-solvent. Suitable cosolvents which can beadded to HFC 134a may be liquids at room temperature or liquefied gasesand include hydrocarbons such as the alkanes, benzene and its esters,low boiling aliphatic esters such as acetates and butyrates, ketonessuch as acetone, methyl isobutyl ketone, methyl ethyl ketone,chlorinated, fluorinated and chlorofluorinated hydrocarbons such asdichloromethane and dichloro difluoromethane, ethers and such asdimethyl ether and diethyl ether, dimethyl formamide, tetrahydrofuran,dimethyl sulphoxide, alcohols such as methyl alcohol, ethyl alcohol,n-propanol, iso-propanol, acids such as acetic acid, formic acid andeven acetic anhydride, nitriles such as acetronitrile (methyl cyanide),anhydrous liquefied ammonia and other liquefied gases such as sulphurdioxide, nitric oxide, nitrogen dioxide, nitrous oxide, liquefiedhydrogen sulphide, carbon disulphide, nitromethane, and nitrobenzenecould all be used in this process.

The most useful co-solvents have proved to be butane and dimethyl ether.Regrettably, though, many of the useful co-solvents which are mixed withHFC 134a re-confer the serious hazard of flammability on the mixturesand therefore raise safety issues. There may, depending on the choice ofco-solvent, be other problems such as environmental issues.

Although it is neither a serious ozone depleter nor a VOC, unfortunatelyHFC 134a is a potent and powerful greenhouse gas. It has a globalwarming potential or greenhouse effect some 8 times as strong as carbondioxide. HFC 134a is very chemically inert and persists in theenvironment for very long periods of time, during its decomposition. Ithas a t½ life between 8.6 and 16.7 years.

Historically solvents such as hexane, petroleum fractions, benzene,methylene chloride (dichloromethane) have been widely used to extractoils from an enormous range of flavoursome oleo-resins, drug containingextracts and fragrant raw materials (“concretes”). These solvents are incommon use even in the engineering, petroleum and mineral industries,where they are often used to de-grease raw materials containing orcoated in oil and to clean metal parts, by the removal of oilylubricating preparations. Useful amounts of oils have even beenextracted from mineral raw materials such as oil shales and tar sandswith such solvents. Even soils contaminated with oily industrial wastemay be remediated with such solvents.

As they are all highly flammable, one disadvantage of conventionalsolvent systems such as hydrocarbon solvents, for example hexane andbenzene and petroleum fractions, has always been the dangers of fire orexplosion and incineration. These solvents also present further hazardsto the operators of such processes because many hydrocarbon andchlorinated solvents are harmful or toxic by inhalation and ingestion.They are frequently carcinogenic and all of the hydrocarbon solventsused in current practice are classed as VOCs (volatile organiccompounds) which are said to have a positive photo-chemical ozonegenerating potential.

A further disadvantage of the most commonly used solvents, hexane and“petroleum ether”, is that their boiling points (at atmosphericpressure) are in excess of 50 degrees Celsius. Hence, in order to removesuch solvents from the solutions of the desired components, the desiredcomponent must either be exposed to high temperatures or high vacuum.Both of these treatments detract from and are damaging and deleteriousto the quality of the desired component or extract. Also, theevaporation of the solvent from the solution of the oil, and the solventrecovery by condensation is expensive on account of the energy costs.

The finished products from such processes are often intended for publicconsumption and the presence of toxic or harmful residues may presentdifficulties when seeking regulatory approval of the finished product.

These problems become even more serious when (as is increasingly thecase) statutory authorities are demanding that the solvent residuelevels in oils sold for use in human food stuffs are required to meetincreasingly stringent requirements such as solvent residue levels ofonly 50, 10 and even 1 part per million. Achieving such levels ofsolvent residue requires that the solution and extract be exposed tovery high vacuum and/or very high temperatures. Such treatment canresult in serious loss of the precious volatile components from theextracts and serious thermal damage to the desirable component.

A strategy to overcome these problems has long been to employhydrocarbon solvents such as butane and even propane (in liquid formunder pressure). However, these processes are even more dangerous, ofcourse, as any leakage of the (usually odourless) solvent vapours fromthe operating equipment, poses a greatly enhanced risk and chance ofexplosion and incineration.

The use of less flammable solvents such as chlorinated hydrocarbonsolvents has gone some way to reducing these risks. For example, the useof methylene chloride (dichloromethane) to extract valuable componentssuch as caffeine from coffee and tea has become common. Similarly,perchloroethylene has a long history of use in the dry cleaning industryto de-grease oily clothing.

However, many of the traditional chlorinated solvents present their ownproblems. Most of these materials are either harmful or toxic or may bedamaging to the environment. Their vapours are believed to deplete theprotective ozone in the stratosphere. Many of these chlorinated solventsare also greenhouse gases and may lead to global warming.

The process and apparatus we now describe in this specification are ofgreat value in the extraction of high quality, desirable components suchas oils, pigments, pharmacologically active ingredients and resins froma wide range of substrates comprising plant, animal and mineral matter,of both terrestrial and marine origin. The same process and apparatus,when using the solvent systems according to an embodiment of theinvention, are able to extract fixed and mineral oils.

The process comprises the contacting of the substrate (such as a bulkraw material) in which the desired component is already contained, witha solvent so as to allow the desired component to dissolve in thesolvent. It provides for the removal and separation of the substratefrom the solution of the desired component in the solvent. It furtherprovides for the removal of the solvent from the solution and itsrecovery for recycling and re-use, and for the harvesting of the solutefrom which the solvent has been removed. The solute—in suchcases—comprises the desired component.

The extraction of desirable components from a substrate in many of theprior art processes must be carried out in sealed (pressure vessel)equipment. In any solvent extraction process it is normally highlydesirable for economic and environmental reasons to collect as much ofthe used solvent from the solution formed (of the solvent and thedesirable component) and from the spent and extracted bulk raw material.Nevertheless it is inevitable that some loss of solvent vapour into theatmosphere always occurs.

This consideration has lead us to search for a solvent which has moreacceptable physiological and environmental characteristics and which isalso an effective solvent capable of extracting fixed, mineral andessential oils.

The present invention thus aims to provide an economical process whichis also able to provide the extracted oils in relatively high yield. Itis also an aim to provide a quick extraction process which can be usedcommercially.

It is also an aim to provide a process which is easy to run and whichdoes not require bulky or complicated apparatus. It is another aim touse a solvent which is not environmentally damaging and which does nothave any significant photochemical ozone generating potential. Such aprocess aims to eliminate or reduce the losses of solvent during theextraction process. Indeed, it is a further aim to provide a process inwhich solvent losses are minimised so that there is substantially 100%solvent recovery.

It is also an aim to avoid the risk of fire or explosion by using anon-flammable solvent system, or at least a system having asignificantly reduced risk of fire or explosion.

It is also an aim to minimise the content of any toxic solvent residuesin the final product and preferably to achieve a product in which thereare substantially no toxic solvent residues. It is an aim that theextracted oil be substantially free of traces of solvent so that theextracted oil may easily satisfy any present or future regulatoryrequirements.

It is also intended to dispense with the need for the elimination of, orevaporation and condensation of, large quantities of solvents in orderto obtain the final product from the solvent.

We have found that iodotrifluoromethane (ITFM) satisfies most or all ofthese requirements.

According to a first aspect of the invention there is provided a methodof extracting oil from an oil-bearing substrate comprising:

-   (a) contacting the substrate with a solvent comprising    iodotrifluoromethane and, optionally, one or more cosolvents to form    a solution of the oil in the solvent;-   (b) separating the solution from the substrate; and-   (c) removing the solvent from the solution to provide the desired    oil.

In a first embodiment of this aspect of the invention the methodcomprises contacting the solvent with the substrate in a first vesseland separating the resulting solution from the substrate by transferringthe solution to a second vessel while retaining the extracted substratein the first vessel.

Preferably the first and second vessels are each sealable and eachinclude an openable and closable valve, the method further comprisingthe steps of:

-   (i) connecting the vessels together to provide a flow path between    the vessels via said valves; and-   (ii) opening the valves of the vessels and causing the solution to    flow from the first vessel to the second vessel.

In a particularly preferred embodiment, the method further comprises thestep of applying heat to heat the solvent in the first vessel. This stepfacilitates the dissolution of the oil in the solvent.

In another particularly preferred embodiment, the method furthercomprises the step of cooling the solution in the second vessel. Thiscooling step can cause the oil to precipitate from the solvent, so thatthe oil and solvent can be separated.

According to a second aspect of the invention there is provided a methodof extracting oil from an oil-bearing substrate comprising:

-   (i) providing an apparatus comprising first and second sealable    vessels, the first vessel including means for retaining said    substrate in the vessel, each vessel having an inlet and an outlet    and being so connected as to provide a fluid flow circuit only in    the direction from the outlet of the first vessel to the inlet of    the second vessel and from the outlet of the second vessel to the    inlet of the first vessel;-   (ii) charging the oil-bearing substrate into the first vessel;-   (iii) charging the apparatus with a solvent comprising    iodotrifluoromethane and, optionally, one or more co-solvents so    that the solvent contacts the substrate and forms a solution of the    oil in the solvent;-   (iv) causing said solution to flow in said fluid flow circuit from    the first vessel to the second vessel; and-   (vi) separating the solvent from the oil in the second vessel and    recovering the oil.

This aspect of the invention provides a continuous process forextracting oil from a substrate.

In a particularly preferred embodiment of this aspect of the invention,the method further comprises the step of applying heat to the solvent inthe first vessel, or adjacent the inlet of the first vessel. Thisheating step facilitates dissolution of the oil in the solvent

In another particularly preferred embodiment, the method furthercomprises the step of cooling the contents of the second vessel. Thiscooling step can cause the oil to precipitate from the solvent forsubsequent separation and recovery.

Preferably the method of this aspect of the invention further comprisesrecovering the separated solvent for use in further extractions.

In particularly preferred embodiments of the first and second aspects ofthe invention, the optional co-solvent is selected from HFC 134a and HFC4310.

Iodotrifluoromethane has the advantage that it has no global warmingpotential and is not a VOC. It is not flammable, indeed actually used asfire extinguisher. It does not deplete the ozone layer, is effectivelynon-toxic and represents virtually no biological hazard or environmentalthreat. It has a very low boiling point (−22.5 degrees Celsius atatmospheric pressure) and a modest vapour pressure of only 63.7 psi (4.3Bar) at 25 degrees Celsius.

ITFM is an excellent extraction medium and solvent for many of the oilsof commerce including triglycerides, fatty acids, sterols and theiresters, natural waxes, hydrocarbons (both straight and branched chainsand cyclic and poly-cyclic) with molecular weights up to severalhundreds. It also dissolves fragrance oils, pigments, flavour oils andmany pharmaceutical components from natural plant and animal rawmaterials. For these uses in the process of the invention, it is notusually necessary to perform a heating step.

ITFM also presents no special problems in handling and recovery forrecycling.

Although ITFM is currently a costly solvent, the financial penaltyattendant on its use may be minimised using the process of the presentinvention since almost complete solvent recovery occurs. Furthermore,the solvent offers tremendous advantages to the environment.

Because it has a low boiling point, extraction of and recovery ofdesirable components can be carried out at room temperature or below,thus eliminating any chance of thermal degradation or damage to theextracts that often occurs when other solvents are used.Iodotrifluoromethane (ITFM) is pH neutral and does not hydrolyseappreciably in water at room temperature.

Should it be necessary to reduce the wide spectrum of solutes whichdissolve in iodotrifluoromethane (ITFM) (i.e. to render it moreselective), it can be mixed with one or more poor or non-solvents.Suitable poor solvents or non-solvents are for example, HFC 134a(1,1,1,2-tetrafluoroethane) or HFC 4310(1,1,1,2,2,3,4,5,5,5-decafluoropentane). This may be done to impartselectivity to the extraction process in order to enhance the amount ofa particular oil in a mixture of extracted oils. In this case, since theco-solvent (such as HFC 134a) only represents a part of the solventmixture (rather than being the sole solvent) any problems which may beassociated with the co-solvent itself are minimised.

A feature of the invention thus makes use of the property of mixtures ofITFM and one or more suitable co-solvents to dissolve to specified andfinite limits of molecular weight or polarity. This confers a degree ofselectivity on the solvent mixtures to extract components of specifiedmolecular weight, such as volatile components of fragrance oils, whilstexcluding from solution many of the materials which would then beconsidered to be undesirable contaminants, such as triglycerides, fattyacids and natural waxes. It is, however, important that the presence ofthe co-solvent still provides a solvent system which meets statutory orother requirements relating to toxicity or other health hazards.

A related feature of this invention also makes use of the observationthat certain mixtures of ITFM with one or more suitable co-solvents donot dissolve fixed oils such as triglycerides, fatty acids, naturalwaxes, mineral oils and petroleum fractions etc at low temperatures. Atelevated temperatures, such solvent mixtures do in fact dissolve thesematerials. Hence it becomes a simple matter to dissolve such fixed andmineral oils and extract them from the substrate such as bulk rawmaterial in which they occur by heating the solvent mixture in thepresence of the substrate. Removal of the heated solution and cooling itcauses the solutes to precipitate from solution in all cases. Thesolutes (being of lower specific gravity than the solvent) float to thetop of the cooled solution and can be easily harvested. In this case,the method would involve the step of elevating the temperature and thestep of cooling the separated solvent solution once it has beentransferred to the second vessel so as to release any dissolved oil. Atthis point, either the released oil or the iodotrifluoromethane solventcan be removed from the second vessel to complete the separation.

The invention also relates to an apparatus for performing oilextraction.

According to a third aspect of the invention there is provided anapparatus for the extraction of oil from an oil-bearing substratecomprising first and second vessels, connecting means providing fluidcommunication between the vessels, at least one closable valve operableto prevent fluid communication between the vessels, the first vesselbeing adapted to receive the oil-bearing substrate and including meansfor retaining the substrate in the first vessel, and, a solvent providedin the first vessel comprising iodotrifluoromethane and, optionally atleast one co-solvent, which solvent may be transferred between the firstand second vessels via the or each closable valve.

In an especially preferred embodiment of this aspect of the invention,each vessel comprises an inlet and an outlet, the outlet of the firstvessel is connected by first connecting means to the inlet of the secondvessel, the outlet of the second vessel is connected by secondconnecting means to the inlet of the first vessel, the first and secondconnecting means include at least one said closable valve, and eachclosable valve is a one-way valve permitting fluid flow in one directiononly, the valves being arranged to provide a fluid flow circuit suchthat the solvent may flow around the circuit in one direction only. Thisembodiment allows a continuous extraction process to be carried out.

Preferably one closable one-way valve is provided at each respectiveinlet and each respective outlet of the first and second vessels. Inthis way, the first and second vessels can be isolated as required.

Preferably the apparatus includes heating means for heating the solventin the first vessel or adjacent to the inlet of the first vessel and/orcooling means for cooling the contents of the second vessel.

In a desirable for the apparatus further comprises a reservoir ofsolvent operatively connectable to the fluid flow circuit. Preferably,the apparatus also includes means for withdrawing solvent from the fluidflow circuit. Desirably, the point for addition of solvent from thereservoir and/or the point for withdrawal of solvent is/are between theoutlet of the second vessel and the inlet of the first vessel.

Preferably the apparatus further comprises means for withdrawing, fromthe second vessel or from the connecting means adjacent the secondvessel, oil which has separated from the solvent.

In a further embodiment, the apparatus includes means for determiningthe pressure in the circuit and/or the temperatures of the first andsecond vessels.

In a further embodiment, the first and second vessels are transparentpressure vessels capable of withstanding pressures of not more than 25bar.

A fourth aspect of the present invention provides a method of extractingoil from an oil-bearing substrate comprising the steps of:

-   (i) contacting the substrate with a solvent comprising    iodotrifluoromethane and, optionally, one or more co-solvents    thereby to dissolve the oil in the solvent; and-   (ii) causing the oil to separate from the solvent to form immiscible    liquid layers of oil and solvent.

Preferably step (ii) involves cooling the solution of oil in thesolvent.

Also preferably step (i) includes heating the solvent.

A fifth aspect of the invention provides a method of extracting oil froman oil-bearing substrate comprising the steps of:

-   (i) contacting the substrate with a solvent comprising    iodotrifluoromethane and, optionally, one or more co-solvents,    thereby to dissolve the oil in the solvent; and-   (ii) allowing the solvent to evaporate at ambient or subambient    temperatures.

In a preferred embodiment of this fifth aspect of the invention themethod further comprises recovering the evaporated solvent andcompressing the solvent to reliquify it.

The present invention also contemplates the use of iodotrifluoromethanefor the extraction of oil from an oil bearing substrate, and also theuse of a solvent comprising iodotrifluoromethane and at least oneco-solvent for the extraction of oil from an oil-bearing substrate.

The present invention further includes an oil obtainable by, or whenobtained by, the method of any of the first, second or fourth aspects ofthe invention.

The present invention also includes a vegetable oil for use infoodstuffs obtainable by or when obtained by, the method of any of thefirst, second or fourth aspects of the invention and containingsubstantially no residue of solvent, especially iodotrifluoromethane.

The appropriate co-solvent, and the iodotrifluoromethane:co-solventratio for a given substance are determined as follows.

An empty bottle together with a removable seal is weighed and the weightrecorded (Weight A). This assembly should be designed to be able towithstand a pressure of say 10 BarG.

Into the bottle is placed a sample of the substance i.e. theoil-containing substrate (raw material) to be extracted, or a sample ofthe oil itself.

The bottle and seal is weighed again and the weight recorded (Weight B).The bottle is then closed and sealed. The difference between weight Band weight A is the weight of the substrate containing oil or the oil.

The iodotrifluoromethane alone is introduced into the bottle and themixture shaken until the contents are homogenous and the solute is incomplete solution. The bottle and contents are weighed again and thefinal weight of the bottle and contents are recorded (Weight C). Thedifference between Weight B and Weight C is the weight of the addediodotrifluoromethane.

Co-solvent in which the solute is only poorly soluble or in which it isinsoluble is then progressively introduced into the bottle. At first noobvious change takes place, but as the quantity of co-solvent isincreased, the contents of the bottle will be seen to turn from crystalclear to opalescent. The weight of the bottle and contents is againrecorded (Weight D). The difference between Weight D and Weight C is thequantity of co-solvent added.

In order to ensure that the precipitation of oil from the mixture hasreached its optimum, the bottle may now be placed in a refrigerator,whereupon the contents will first become cloudy and soon a clear anddistinct layer of oil will separate and float on the lower layer ofclear solvent. The solvent at low temperature can then be withdrawn andintroduced to another bottle charged with more of the oil or theoil-containing substrate (raw material). This cold solvent will notdissolve the oil, but on warming, it will be seen to form a homogeneoussolution (which will itself separate again into two layers on cooling).

This procedure will allow calculation of the composition of a solventmixture. For example: The total weight of solvent used is D−B. Theweight of iodotrifluoromethane is C−B and the weight of co-solvent isD−C.

Hence the weight % composition of the solvent is:iodotrifluoromethane=(C−B/D−B)×100%co-solvent=(D−C/D−B)×100%

The % concentration of solute in the solution=(B−A/D−A)×100%

The invention will now be described with reference to FIG. 1 which showsan apparatus suitable for continuous extraction of fixed and mineraloils according to one embodiment of the process of the presentinvention.

Two vessels (1) and (2) equipped with closable valves were coupledtogether via two sets of tubing (3, 4). Both vessels are capable ofwithstanding pressure typically up to 25 bar. Below vessel (1), thetubing (3) was in the form of a coil (5) sitting in a bath of liquid (6)which could bc heated and maintained at a pre-selected temperature. Thecoil of tubing (5) could, however, be heated by another means or vessel(1) could be heated directly.

Vessel (1) was equipped with internal filters (7) at both ends, whereasvessel (2) was equipped with a filter (8) only at the lower end.

The second vessel (2) was surrounded by coils (9) containing a flow ofcooling liquid and the outside of the coils was insulated. Other meansof cooling vessel (2) could also be used, for example a stream ofcooling gas or a cooling bath.

The circuit was furnished with an inlet (10) and outlet (11) valves forsolvent. During operation of the equipment, the inlet valve was coupledto a solvent reservoir (12) which could be used to both fill the systemwith solvent and maintain the level of solvent during operation. Outletvalve (11) was provided to enable the system to be drained.

At the top of vessel (2), a valve (13) is fitted to facilitate therecovery of oil when this becomes necessary or desirable. A pressuregauge (16) may be provided in the circuit.

The same equipment can be used regardless of whether the solvent isiodotrifluoromethane alone or in combination with a co-solvent, andregardless of whether any heating or cooling is actually performed.

The operation of the equipment is for the purpose of illustration onlydescribed as follows in relation to a mixture of iodotrifluoromethaneand a co-solvent to extract a fixed oil.

-   1. Vessel (1) (which has removable end caps) is charged with the    substrate from which oil is to be extracted (usually in the form of    a finely divided particulate solid). The end caps and filters are    then replaced. The vessel is then connected to the remainder of the    equipment. Air is then removed from the sealed equipment at this    stage.-   2. The equipment (now fully sealed) is then fully charged with    solvent from the bulk solvent storage tank (12) (which remains    connected to the equipment throughout the operation).-   3. The heating bath (6) is then filled with water or oil and the    heating means turned on if required.-   4. If required, cold liquid or gas is circulated round the cooling    coils (5) causing the temperature of the second vessel (2) (and its    contents) to cool.

As the temperature of the liquid in the heating bath rises, so does thetemperature of solvent in the tube below vessel (1). This, of course,causes hot solvent in vessel (1) to rise through the oil containingsubstrate of the vessel (I) due to natural convection.

The substrate is restrained inside vessel (1) by the filters (7)disposed at the top and bottom. The liquid displaced upwards is replacedby cold liquid falling through vessel (2) due to convection.

The entire liquid in the circuit thus becomes mobile and circulating. Ashot liquid passes up through the substrate of vessel (1) oil is exactedfrom the substrate. As the solution enters the top of vessel (2) it iscooled and its solute (the oil) precipitates out of solution.

Alternatively, in the absence of heating and the resulting convectioncurrents which occur, the solvent may be pumped around the circuit.

Because the oil is lighter than the solvent, it floats to the top ofvessel (2) and collects there as it is not able to pass out of thebottom of vessel (2).

When it is considered that sufficient oil has been extracted, all thevalves are closed except valve (14) (the inlet valve for vessel (2)) andvalve (15) (the outlet valve for vessel (2)). Valve (13) is then openedto release the oil and the oil can be decanted into a bottle.

The system may be emptied after use by allowing solvent to drain out ofvalve (1) into a suitable container for recycling and recovery byevaporation.

It will be immediately apparent to one versed in the art, that thisprocess is capable of producing oil without any evaporative step. Sinceevaporation of the solvent is one of the major costs involved in moretraditional methods of extraction, this constitutes a major improvementin the extraction of such oils and represents a significant cost saving.

Since iodotrifluoromethane is neither flammable, nor toxic, norenvironmentally damaging and (in normal operation) is never releasedinto the environment, the process of the present invention represents asignificant improvement over current technologies.

In another embodiment of the process (not shown), the apparatuscomprises two sealable vessels (which are preferably transparent andmade of strengthened or reinforced glass) each being capable ofwithstanding a pressure of up to 20 bar or even 25 bar. Each vessel isequipped with a closable valve which acts as an inlet and an outletvalve. One vessel is also equipped with a removable filtering device,such as a wire gauze or wire wool to prevent the exit of raw materialfrom the vessel at the same time as the solvent is withdrawn.

The two vessels are connected to each other via their inlet/outletvalves so as to form a sealed unit. Typically each vessel is 50 ms to2000 mls capacity, and preferably 100 mls to 500 mls. Such an apparatusis easily assembled and handled. However, there are no particularlimitations other than the usual practical limitations, on the uppersize of such apparatus.

In this embodiment (not shown), it is possible to extract a fixed ormineral oil from a substance in an apparatus comprising two vesselswhich is not arranged in the form of a circuit. The substrate (rawmaterial) is placed in a first vessel and the extraction medium (i.e.the solvent) is also introduced into the first vessel. The inlet/outletvalve of both vessels are then closed and the ensemble is warmed,typically to 40°-60° (and preferably not more than 50° C.), in an ovenor using other suitable heating means. The apparatus may be agitatedduring heating or may contain agitation means such as a magnetic flea.

After an appropriate residence time at the elevated (holding)temperature, typically in the range 1 to 20 minutes and preferably inthe range 3 to 8 minutes from the point of view of efficiency and costeffectiveness, the solution is transferred from the first vessel to thesecond vessel and the ensemble is cooled to room temperature or lower.Ideally, the ensemble is cooled to a temperature in the range −10° to25° C. and preferably in the range 0° to 20° C. Cooling below −10° C. ispossible but increases the costs and complexity of the process.

Transfer of the solution is achieved via the inlet/outlet valves and theraw material remains in the first vessel on account of the filter. Thevalves are closed following transfer of the solvent and before coolingis commenced.

On cooling, the extracted oil precipitates out of solution and begins toaggregate. Since the extracted oil is invariably significantly lessdense that the solvent medium the extracted oil floats on the top of thesolvent layer as a separate immiscible/insoluble layer. The extractedoil can thus be easily separated by decanting. The solvent, which isalmost entirely free of the oil, can then be returned to the firstvessel for use in a further extraction cycle. This process can berepeated several times if desired. From a practical point of view, 10cycles is the upper limit with 3 to 5 cycles being preferred on thebasis of efficiency and time.

This manual procedure though highly effective, was somewhat tedious tocarry out and the whole process is preferably performed as a continuousoperation as described above.

Temperature Difference Between Vessels (1) and (2)

For maximum economic use of equipment designed to prepare extracts suchas those of interest such as fixed or mineral oils, it is beneficial tooperate vessels (1) and (2) at widely dissimilar temperatures. (Thedifference between these temperatures is commonly referred to as “ΔT”).The larger the “ΔT” the better the equipment will perform.

However, limits on “ΔT” are imposed by the design and fabrication of theequipment.

Upper limit of Operating Temperature of Vessel (1)

When iodotrifluoromethane is used, whether mixed with another solvent ornot, a rise in the temperature of operation of Vessel (1) willautomatically cause an increase in the pressure (vapour pressure) withinthe sealed system. Indeed, the highest operating temperature of vessel(1) must obviously never exceed, and must be less than, the “criticaltemperature” of the solvent (mixture) in use.

Also this highest operating temperature would be limited to atemperature less than that above which damage to the raw-material or theextract might occur.

Lower Limit of Operating Temperature of Vessel (2)

The operating temperature of Vessel (2) must be as low as can beconveniently arranged. Sub-ambient and even refrigeration temperaturescan be used.

The lower limit of operation of Vessel (2) will be determined by thecharacteristics of the solution (and its ability to dissolve solute).The solute must dissolve in the solvent as “poorly” as can be arrangedand the “poverty” of this dissolution can be enhanced by lowering thetemperature of operation of Vessel (2). The low limit is also governedby the viscosity of the resulting oil since at very low temperaturessome oils may become difficult to handle.

The operation of the equipment is described for the purpose ofillustration only as follows in relation to the extraction of anessential i.e. volatile oil: the substrate containing the essential oilis introduced into an extractor, having the shape of a flanged tube andfurnished with removable end caps, each of which comprises a plate and asheet of stainless steel mesh secured thereon to form a filter. The endcaps or plates are also equipped with a port which is capable of closureand through which both gases and liquids can pass via the stainlesssteel filter mesh.

The extractor is closed and air is pumped out to a pressure of less than40 mbar. A source of supply of liquid iodotrifluoromethane is connectedto the extractor and liquid solvent is allowed to pass to the extractor.The contents of the extractor are thus bathed in iodotrifluoromethane.The extractor is then sealed as the source of iodotrifluoromethane isdisconnected. The extractor is then tumbled on its lateral axis for aperiod of time to ensure intimate contact between the solvent and thesubstance.

After the tumbling has stopped, the outlet is connected via alternativepipework to a small evaporator which has previously been evacuated to apressure of 40 mbar. The solution of oil in the iodotrifluoromethanesolvent is allowed to pass intermittently from the extractor into theevaporator, to retain a level of liquid and gas filled headspace in theevaporator. The evaporator is then connected to the inlet of acompressor which is allowed to withdraw iodotrifluoromethane gas fromthe head space of the evaporator and to compress the gas (on its outletside) to a pressure in excess of 5 bar.

A this pressure, and at room temperature, the gas is reliquefied and caneither be recycled to the extractor to flush out residual oil or bereintroduced to the original reservoir of solvent for re-use on afurther bath.

Inevitably, during this process the evaporator cools to very lowtemperatures and it is desirable to immerse it in a water bath furnishedwith an immersion heater and a thermostat. The thermostat can be set toactivate the immersion heater when the water temperature falls to forexample 10° C. and to switch off the heater whenever the temperature ofthe water exceeds for example 12° C. In this manner, the evaporator maybe operated at about 10° C. and the vapour pressure is 1 to 3 bar at thecompressor inlet.

The pressure contained the evaporator throughout this process is in theregion of 206 kPa (30 psi). Once all the solution has passed from theextractor to the evaporator, and all the solvent from both the extractorand the evaporator has been evaporated, the vapour pressure inside theevaporator begins to fall.

When this pressure had fallen to just above 0 kPa (0 psig) an outlet onthe bottom of the evaporator is opened so the oil solute (the extract)can run into a suitable receptacle.

Weighing of the receptacle before and after the introduction of the oilreveals the yield of fragrant oil.

Following removal of the oil, the compressor can be allowed to continueto suck residual solvent vapour from the extractor and from thesubstrate within it. By the time the pressure within the extractor hasfallen to 100 mbar over 99.9% of the iodotrifluoromethane solvent willhave been returned to the original reservoir.

To improve the recovery of the solvent the extractor and the extractedsubstrate can be heated.

The present invention will now be illustrated by means of the followingexamples.

EXAMPLE 1

At an ambient temperature of 20 degrees Celsius, 140 grams of peanut oilwere introduced into a PET bottle of capacity 2500 ml and designed towithstand 10 BarG. The bottle was fitted with an aerosol valve. This oilwas dissolved in 780 grams of iodotrifluoromethane which was introducedinto the bottle, via the aerosol valve, from a bulk container.

The solution formed was crystal clear and pale yellow in colour. Itformed a completely homogeneous solution, a single phase.

HFC 134a was then introduced into the bottle via the aerosol valve froma similar bulk storage container, until the mixture separated into twodistinct layers. The bottle was weighed to ascertain how much HFC 134ahad been added. This proved to be 440 grams of HFC 134a. The upper layerof the two phase system was yellow and clear. The lower layer was clearand water white.

Warming this two phase mixture to 42 degrees Celsius with gentleagitation for a few seconds, caused it to become clear. It formed asingle phase homogeneous solution.

Upon cooling, a two phase system re-formed, with the yellow layer lyingon top of a clear water white layer.

The composition of the solvent in this case was 36.1% HFC 134a:63.9%ITFM w/w.

EXAMPLE 2

At an ambient temperature of 20 degrees Celsius, 140 grams of peanut oilwere introduced into a PET bottle similar to that of Example 1. On thisoccasion, 810 grams of iodotrifluoromethane were introduced into thebottle via the aerosol valve. A yellow, bright homogeneous solution wasobtained.

On this occasion, 440 grams of HFC 134a were introduced into the bottle.The contents of the bottle remained as a single phase, slightlyopalescent solution.

Cooling this solution to 4 degrees Celsius caused it to separate into a“two phase” system. The upper layer being yellow and the lower layerbeing clear and water white. Allowing this mixture to warm to roomtemperature (20 degrees Celsius) with gentle agitation, caused the twophase mixture to revert to its original state as a single phase,homogeneous (if slightly opalescent) solution.

The composition of the solvent in this case was 35.3% HFC 134a:64.8%ITFM w/w.

EXAMPLE 3

224 grams of finely ground sesame seeds were introduced into a 2500 mlcapacity PET bottle fitted with an aerosol valve, at an ambienttemperature of 20 degrees Celsius. 780 grams of iodotrifluoromethane wasintroduced to the bottle via the aerosol valve from a bulk container.

Shaking the bottle caused a distribution of the sesame seed paste. Thebio-mass floated to the top as the specific gravity of the ITFM is closeto 2.0 To this mixture was added 480 grams of HFC 134a. Placing thismixture in the fridge at 4 degrees Celsius caused agglomeration of thebio-mass. A single lump of solids was obtained which could not be easilybroken up with shaking. This was assumed to be due to the precipitatedoil and sesame seed biomass becoming remixed.

Allowing this mixture to warm to room temperature caused re-dissolutionof the oil and the sesame seed bio-mass was then much easier to dispersein the liquid.

The liquid phase of this mixture was harvested by inverting the bottle,via a filter attached to the aerosol valve, into a second PET container.A clear homogeneous liquid was obtained.

Refrigeration of this liquid caused it to separate into two layers. Bothlayers could be harvested separately (by inverting the bottle) and thelower layer was found to contain mostly solvent whilst the upper layercomprised mostly oil (with a little solvent dissolved in it).

The composition of the solvent in this case was 38% HFC 134a:62% ITFMw/w.

EXAMPLE 4

20 grams of peanut butter (Sun Pat) were introduced into a 210 mlcapacity PET bottle fitted with an aerosol valve and filter. 195 gramsof ITFM were added. The mixture formed a cream coloured, evendispersion. 101 grams of HFC 134a were then added and the mixtureshaken. The solution was filtered into a new PET bottle. 274 grams ofsolution were recovered.

To this solution was added a further 7 grams of HFC 134a. It remained asa single phase.

A further 5 grams of HFC 134a were added. The mixture was nowrefrigerated and two distinct layers formed. The lower layer of thissolution was recovered and added to a further 141 grams of peanut butterat 20 degrees Celsius. A milky even dispersion of creamy coloured peanutbiomass was formed. This mixture was again filtered back into the bottlein which the solution had originally been filtered and the combinedfiltrates were again refrigerated.

Refrigeration of this solution caused a great deal of oil to precipitateout of solution and a thick layer of yellow oil formed on the surface.This oily material was easily recovered by inverting the bottlefollowing the removal of the lower (largely solvent) layer.

The composition of the solvent in this mixture was 37% HFC 134A:63% ITFMw/w.

EXAMPLE 5

28 grams of ground roasted cocoa beans were placed into a 210 mlcapacity PET bottle and an aerosol valve with filter was attached. 189grams of IIFM were added and 106 grams of HFC 134a.

The mixture was filtered into a second bottle and refrigerated to minus10 degrees Celsius. White, solid, cocoa butter was seen to rise to thesurface. Re-warming of this bottle to room temperature caused the cocoabutter to melt, redissolve and become homogeneously distributedthroughout the liquid phase.

The composition of the solvent in this mixture was 36% HFC 134a:64% ITFMw/w.

The present invention thus addresses many of the disadvantages discussedabove and provides a means of obtaining fixed oils and mineral oils ingood yields in a form approaching 100% purity.

1. A method of extracting a component selected from oils, pigments,pharmacologically active ingredients and resins from a substance bearingthe component, comprising: (a) contacting the substrate with a solventcomprising iodotrifluoromethane and, optionally, one or more co-solventsto form a solution of the component in the solvent; (b) separating thesolution from the substrate; and (c) removing the solvent from thesolution to provide the desired component.
 2. A method as claimed inclaim 1 further comprising contacting the solvent with the substrate ina first vessel and separating the resulting solution from the substrateby transferring the solution to a second vessel while retaining theextracted substrate in the first vessel.
 3. A method as claimed in claim2 wherein the first and second vessels are each sealable and eachinclude an openable and closeable valve, the method further comprisingthe steps of: (i) connecting the vessels together to provide a flow pathbetween the vessels via said valves; and (ii) causing the solution toflow from the first vessel to the second vessel.
 4. A method as claimedin claim 2 further comprising the step of applying heat to heat thesolvent in the first vessel.
 5. A method as claimed in claim 2 furthercomprising the step of cooling the solution in the second vessel.
 6. Amethod as claimed in claim 1 including an additional step, after step(a), of adding one or more further solvents to the solution of thecomponent in the solvent comprising iodotrifluoromethane so as to reducethe spectrum of solutes dissolved.
 7. A method according to claim 6wherein the further solvent is selected from 1,1,1,2-tetrafluoroethaneand 1,1,1,2,2,3,4,5,5,5-decafluoropentane.
 8. A method of extractingcomponent selected from oils, pigments pharmacologically activeingredients and resins from a substrate bearing the componentcomprising: (a) providing an apparatus comprising first and secondsealable vessels, the first vessel including means for retaining saidsubstrate in the vessel, each vessel having an inlet and an outlet andbeing so connected as to provide a fluid flow circuit only in thedirection from the outlet of the first vessel to the inlet of the secondvessel and from the outlet of the second vessel to the inlet of thefirst vessel; (b) charging the substrate bearing the component into thefirst vessel; (c) charging the apparatus with a solvent comprisingiodotrifluoromethane and, optionally, one or more co-solvents so thatthe solvent contacts the substrate and forms a solution of the componentin the solvent; (d) causing said solution to flow in said fluid flowcircuit from the first vessel to the second vessel; and (e) separatingthe solvent from the component in the second vessel and recovering thecomponent.
 9. A method as claimed in claims 1 or 8 wherein the optionalco-solvent is selected from 1,1,1,2-tetrafluoroethane and1,1,1,2,2,3,4,5,5,5-decafluoropentane.
 10. A method as claimed in claim8 further comprising the step of applying heat to the solvent in thefirst vessel, or adjacent the inlet of the first vessel.
 11. A method asclaimed in claim 8 further comprising the step of cooling the contentsof the second vessel.
 12. A method as claimed in claim 8 furthercomprising recovering the separated solvent for use in furtherextractions.
 13. A method according to claim 8 including an additionalstep, after step (c), of adding one or more further solvents to thesolution of the component in the solvent comprising iodotrifluoromethaneso as to reduce the spectrum of solutes dissolved.
 14. A methodaccording to claim 13 wherein the further solvent is selected from1,1,1,2-tetrafluoroethane and 1,1,1,2,2,3,4,5,5,5-decafluoropentane. 15.A method of extracting oil from an oil bearing substrate comprising thesteps of: (i) contacting the substrate with a solvent comprisingiodotrifluoromethane and, optionally, one or more solvents thereby todissolve the oil in the solvent; and (ii) causing the oil to separatefrom the solvent to form immiscible liquid layers of oil and solvent.16. A method as claimed in claim 15 wherein step (ii) involves coolingthe solution of oil in the solvent.
 17. A method as claimed in claim 15wherein step (i) includes heating the solvent.
 18. A method according toclaim 15 including an additional step, after step (i), of adding one ormore further solvents to the solution of oil in the solvent comprisingiodotrifluoromethane so as to reduce the spectrum of solutes dissolved.19. A method according to claim 18 wherein the further solvent isselected from 1,1,1,2-tetrafluoroethane and1,1,1,2,2,3,4,5,5,5-decafluoropentane.
 20. A method of extracting acomponent selected from oils, pigments, pharmacological activeingredients and resins from a substrate bearing the component,comprising the steps of: (i) contacting the substrate with a solventcomprising iodotrifluoromethane and, optionally, one or moreco-solvents, thereby to dissolve the component in the solvent; and (ii)allowing the solvent to evaporate at ambient or sub-ambienttemperatures.
 21. A method as claimed in claim 20 further comprisingrecovering the evaporated solvent and compressing the solvent tore-liquify it.
 22. A method according to claim 20 including anadditional step, after step (i), of adding one or more further solventsto the solution of the component in the solvent comprisingiodotrifluoromethane so as to reduce spectrum of solutes dissolved. 23.A method according to claim 22 wherein wherein the further solvent isselected from 1,1,1,2-tetrafluoroethane and1,1,1,2,2,3,4,5,5,5-decafluoropentane.
 24. A method of extracting acomponent selected from oils, pigments, pharmacologically activeingredients and resins from a substrate bearing the component comprisingusing iodotrifluoromethane as a solvent for extraction.
 25. An apparatusfor the extraction of component selected from oils, pigments,pharmacologically active ingredients and resins from a substrate bearingthe component, comprising first and second vessels, connecting meansproviding fluid communication between the vessels, closable valvesoperable to prevent fluid communication between the vessels, the firstvessel being adapted to receive the substrate bearing the component andincluding means for retaining the substrate in the first vessel, and, asolvent provided in the first vessel comprising iodotrifluoromethaneand, optionally, at least one co-solvent, which solvent may betransferred between the first and second vessels via the closeablevalves; wherein each vessel comprises an inlet and an outlet, the outletof the first vessel is connected by first connecting means to the inletof the second vessel, the outlet of the second vessel is connected bysecond connecting means to the inlet of the first vessel, the first andsecond connecting means include closable valves, and each closable valveis a one-way valve permitting fluid flow in one direction only, thevalves being arranged to a provide a fluid circuit such that the solventmay flow around the circuit in one direction only; and wherein oneclosable one-way valve is provided at each respective inlet and eachrespective first and second vessels.